1. Field of the Invention
The present invention relates generally to a system that may be used in conjunction with chucks, and, more particularly, to a system and method for securing a semiconductor wafer substantially flat on a chuck and a system and method for cooling a heated chuck.
2. Disclosure of Related Art
Chucks have long been used to fixedly hold semiconductor wafers during testing. Each semiconductor wafer may contain several thousand integrated circuits on a wafer surface that must be tested. Probers having a chuck and a probe card are utilized to make electrical contact with the integrated circuits. Electrical test signals can be transmitted from testers via the probe card to the integrated circuits. The probe cards contain conductive probe needles that make contact with force on conductive test pads disposed on each integrated circuit. The needles contacting the test pads are commonly referred to as "probing."
In at least one known wafer holding system, a vacuum source is connected to a chuck having a plurality of holes to create a vacuum force for holding a wafer against the chuck. However, the known systems have several problems. First, the known systems do not allow for a relatively soft engagement between the chuck and a wafer when the vacuum force is initially induced. The known systems induce a vacuum force that may slam the wafer against the chuck. Slamming the wafer against the chuck may create surface cracks on the wafer resulting in scrapped integrated circuits. Second, the known systems will not pull down a warped wafer resting on the chuck so that it is substantially flat against the chuck. It is essential during wafer testing that the wafer be held flat against the chuck. Holding the wafer flat allows the probe needles to make adequate electrical contact with the integrated circuit test pads. Otherwise, erroneous integrated circuit test failures will occur during testing. Third, the known systems will not quickly cool down a heated chuck used for "hot chuck testing" the wafers. Utilizing known systems, after hot chuck testing the wafers, the chuck must sit idle until it cools to an ambient temperature. Thereafter, the chuck can be used to test wafers at an ambient temperature. Cooling a heated chuck using the ambient atmosphere may take several hours resulting in manufacturing downtime and associated manufacturing costs.
The present invention addresses the need for providing greater control over the wafer flattening process such that the surface of the semiconductor wafer is rendered essentially flat without damaging the wafer. The present invention also addresses the need for cooling a heated chuck relatively quickly as compared with known methods.